The present invention relates to tire construction and manufacturing of pneumatic tires, in general, and more particularly, to an improved pneumatic tire structure characterized by reduced cost of materials and ease of manufacture and improved performance.
Pneumatic tires for vehicle wheels are, of course, well known. Among the popular styles of pneumatic tires which have gained commercial acceptance are bias tires and radial tires. In each of these tires, cords, usually made of rayon, nylon, polyester, steel, glass or aramid filaments, are imbedded in the elastomeric carcass of the tire. In the radial tire, the cords in the elastomeric tire carcass are disposed in side-by-side parallel position and extend from bead to bead over the crown of the tire at an angular relationship of approximately 90 degrees relative to the peripheral centerline of the tire carcass and may be thought of as being positioned as radial spokes when viewing the tire carcass from a side elevation position. In a bias tire, the cords in the tire carcass are also positioned in a side-byside parallel position, out at an angle of approximately 40 degrees relative to the peripheral centerline of the tire carcass although other angular relationships are contemplated when referring to a tire as a bias tire.
In either event the tire carcass is typically provided with one or more peripheral plies or belts around the outer circumference of the tire carcass. Particularly in the case of the radial ply tire, these plies or belts are formed of an elastomeric material also having side-by-side parallel cords embedded therein. The cords may be oriented perpendicular to the peripheral centerline of the tire or at an angle or bias to the peripheral centerline of the tire carcass outer circumference. The tire tread is positioned on top of these circumferential plies. Tires constructed in such manner fall into the category of restricted periphery tires.
Steel or textile cord belted radial tires have certain speed and performance characteristics which have made such tires extremely desirable for use on a variety of ground vehicles and aircraft. However, these speed and other performance characteristlcs are achieved at substantially higher costs not only for the raw materials used in the tire, but also in the tire manufacturing process. Thus the decision to use, for example, a steel cord belted radial tire on a particular vehicle and for a particular purpose, requires a balancing of cost with the performance characteristics which the tire is expected to achieve.
There are numerous specialty vehicles such as golf cars, lawn and garden tractors, vehicles or machines, riding lawn mowers, utility and recreational vehicles, all-terrain and off-the-road vehicles which do not require periphery restricted tires which provide the same speed and performance characteristics as for passenger cars, trucks and aircraft. In addition, these specialty vehicles weigh less than the other types of vehicles mentioned above. The periphery unrestricted tires which are the subject of this invention, which are the opposite of the conventional periphery restricted radial tires, feature reduced weight while still being fully safe and fully suitable for application on the specialty vehicles indicated above.
U.S. Pat. No. 3,570,573, to Marker, et al., issued in 1971, discloses a structural ply for a pneumatic tire, where the ply includes parallel, periphery continuous, restricting cords embedded in an elastomeric compound, in combination with uniformly dispersed, oriented short fibers also disposed in the elastomeric compound. Thus, the restricting ply or plies includes both cords and fibers. A distinction should now be made between "cord", "yarn" and "filament", as those terms are understood by those of ordinary skill in the art. Cords are understood in the tire industry structurally, as being made up of a series of continuous strands of material, with a strand, in turn, being a gathered plurality of continuous filaments. The filaments are wound or twisted together to form a strand, and the strands are twisted or cabled to form a cord. A filament is understood in the tire industry to refer to a single, individual fiber. (See, generally, the aforementioned U.S. Pat. at column 3, line 70, through column 4, line 4) Both the filament and the cord, of course, may be made of rayon, nylon, polyester, glass, cotton or metal.
U.S. Pat. No. 3,570,574, to Marker, et al., issued in 1971, also discloses a structural ply for a pneumatic tire where the peripheral plies or belts include cords and chopped fibers to restrict the tire carcass against peripheral expansion.
U.S. Pat. No. 3,570,575, to Marker et al. issued in 1971, also discloses circumferential plies where the elastomeric material includes both cords and filaments, again, with certain orientation of the cords and filaments described in the patent.
Canadian Patent 889,677 of Jan. 4th, 1972, illustrates and describes a pneumatic tire with peripheral plies formed of an elastomeric material have parallel, discontinuous cords embedded therein. The cords are oriented parallel to each other and parallel to the peripheral centerline of the tire.
U.S. Pat. No. 3 772,130, to Marzocchi, issued in 1973, also discloses a ply configuration which includes both cords and filaments, again with specific orientation of both cords and fibers as described therein.
U.S. Pat. No. 3,799,233, to Cappa, issued in 1974, illustrates a tire construction where it appears that both plies and breakers are provided, the breakers being of elastomeric material and including small oriented particles of a articular modulus of elasticity, such as glass, again oriented at a specific angle as described therein.
U.S. Pat. No. 3,918,506, to Marzocchi, issued in 1975, illustrates an improved tire construction including multiple plies, one of cords and the other of filaments, strands, yarn or cords.
Lastly, U.S. Pat. No. 4,067,372, to Masson, issued in 1978, illustrates the use of "shoulder" plies in addition to circumferential plies, the shoulder plies being an elastomeric material and including fibers therein.
Each of the above patents are incorporated by reference and the foregoing brief summary is not intended to be an exhaustive explanation of the teachings or variations described therein.
As may be appraciated from a brief review of these eight prior patents, the vehicle tires as described therein are all of the restricted periphery type and, consequently, to be called so, each typically requires peripheral cords, alone or with peripheral fibers, or circumferential plies and shoulder plies, or other expensive variations thereof to achieve tire carcass outer periphery restriction. Prior to the present invention, however, no attention has been paid to the particular vehicle operational requirements and to reducing the cost of manufacture of the specialty tire, such as the tire for a golf car, lawn or garden tractor, etc., by eliminating tire carcass peripheral restricting cords while still maintaining many of the benefits of the cord reinforced, radial restricted periphery belted tire.